996 PSM and ABS lights coming on when dropping a gear?

[RodMod]

Evening,

I have been using my Mums 2001 996 Carrera 4 for a couple of weeks. Yesterday, I dropped a gear (tiptronic box) and gave it a bit of welly and the PSM and ABS lights came up on the dash. I pulled over and turned the car off, and when I restarted the car the lights had gone out?

Anyone had this happen or know why its doing this?

Thanks

Rod.

[thegoose]

This may sound odd but it's highly likely that the MAF needs replacing. It's easy to test, open the engine cover and slightly right of centre there's an electrical connector on the induction pipe - unplug it and the car will still run on baseline settings, ignoring the info from the MAF signal which it would normally use to fine tune itself. If you don't get the current symptoms with the MAF unplugged then you need a new one - 2 security Torx bolts is all you need to remove to swap it over.

[RodMod]

thegoose said:

This may sound odd but it's highly likely that the MAF needs replacing. It's easy to test, open the engine cover and slightly right of centre there's an electrical connector on the induction pipe - unplug it and the car will still run on baseline settings, ignoring the info from the MAF signal which it would normally use to fine tune itself. If you don't get the current symptoms with the MAF unplugged then you need a new one - 2 security Torx bolts is all you need to remove to swap it over.

Thank you for that I'll have a look tomorrow.

Rod.

[Pope]

Brake light switch if not.......

[Polome]

Had a very similar problem on my old 996 a few years ago...turned out one of the reluctor rings for the ABS had corroded badly and had separated from it's mounting on the axle and was periodically slipping and loosing rotation speed during hard acceleration. The fault was hard to diagnose , OPC plugin showed a faulty ABS sensor ,which was replaced but did not fix fault...then the speedometer numbers started to wander duriing acceleration . Further investigation showed the reluctor ring was loose..it was the first time my local OPC had seen this fault, my car was ten years old at the time but it was surprising how badly the ring had corroded.....I'm no expert but think you need car plugged in for diagnosis...good luck. Ian

[Moosh]

Pope said:

Brake light switch if not.......

As above is the normal cause. Let us know how you get on

[monthefish]

Lots of possible causes.

Mine was leaking vacuum pipes on my 996t.

[RodMod]

Evening all,

update, I took the car out Sunday evening and the lights are no longer coming up when accelerating. I don't know if this will be the same tomorrow but Its been used a few .evenings this week it seems to be cured.

If it happens again I will start with the MAF then go on to the brake light switch.

Thank you for your help chaps.

[davek_964]

I don't think unplugging the MAF will help you much unless you also have some running problems. If you do, then unplugging it so it uses default values might prove its the cause. But otherwise, unplugging it simply will cause those warning lights to be displayed - that won't prove its what is causing them when it is plugged in.

MAF was the cause with my turbo, but when they came on it coincided with a big engine stutter.

[thegoose]

Unplugging the MAF won't cause the lights to come on. They may come on, but if they do you've effectively eliminated the MAF as the cause.

[davek_964]

thegoose said:

Unplugging the MAF won't cause the lights to come on. They may come on, but if they do you've effectively eliminated the MAF as the cause.

On my turbo, unplugging the MAF did cause those lights to come on. I unplugged mine a couple of times to investigate running problems in the 5 years I owned it, and it always resulted in those warning lights until it was plugged back in.

[Munich]

I will be reading this thread with interest because I have been having the same problem with my 996 (also a tiptronic). The PSM/ABS lights first lit up about 6 months ago and with the exception of a couple of random weeks have been on the whole time since. I've locked up the inside front wheel a couple of times too so the ABS has definitely not been working.... I went to take it in today to be looked at and typically the lights weren't illuminated.

[thegoose]

davek_964 said:

On my turbo, unplugging the MAF did cause those lights to come on. I unplugged mine a couple of times to investigate running problems in the 5 years I owned it, and it always resulted in those warning lights until it was plugged back in.

My post was in relation to the OP's question and the car he has - a Carrera 4. Turbos obviously behave differently from what you say, which is interesting to know.

[belfry]

Did you wash the car beforehand? My old 964 would flash some abs warning lights when the sensors were wet after washing the car.